Why IS CDT Testing Better Than Other Liver Tests Like GGT?

Once again Kings College London (KCL) led the way for this excellent piece of research. For decades GGT (gamma-glutamyltransferase) was the classic liver enzyme to test to show liver damage and therefore indicate who (sometimes wrongly) was an alcoholic. It was time to change this so in 2011, KCL compared GGT to CDT in almost 360 people from 3 groups - those admitted with alcohol dependency, those with harmful alcohol misuse and regular social drinkers not on any treatment. They were all compared to a control group but who had medical problems that usually confuse or alter blood tests, such as liver disease and diabetes.

The results were pretty clear. CDT had a much larger Positive Predictive Value (PPV) which shows how well a test will do in predicting the condition in a normal population compared to GGT. The CDT PPV was even better in the fourth group of people with medical conditions.

So all in all, the DVLA was happy that they had a test which worked better not only in normal people but also would not be affected in those with existing medical conditions. When CDT was put to test in a pilot project in 2011 with actual High Risk Offenders (HROs) it did well especially with drivers who were difficult to diagnose because of other confusing factors. The pilot tested 1223 drivers and was able to make strong decisions about whether they should be prevented from driving, needed regular reviews with CDT testing or could return back to driving, as was the case for 85% of those assessed. The DVLA concluded.......

“this more accurate (CDT) test has resulted in quicker decisions, fewer appeals against licensing decisions, a greater ethos of evaluation and more research”

The take home message here is that CDT is the best we have out there so far for picking up those who drink more and often than they should and is not affected as much by other conditions.